Paralleling Nixies

[peter bunge]

Question 1. Has anyone tried paralleling two or three Nixies from a single 74141?

I am making a working demonstration with a variety of vintage displays (Nixie, Dekatron, Numitron, Amperex 8453,etc) that will all count together from a common clock.

 

Question 2.  The data sheet for the IN16 says:

8. If the indicator is used in such a place that it is not being affected by other sources of

light and the effect of the surrounding energy sources is lessened due to the indicator

being encased in a metal capsule, in order to avoid the possible increase in the voltage

and the ready-time of the indicator (the time it takes for the indicator to display the digits), it is recommended that you use artificial lighting with a luminosity level of not less than 40 lumens or one of the “comma” symbols as a “pilot” electrode with a current

in its circuit of 0.7—1.5 μΑ.

which helps explain a question about Nixies that do not fire in the dark. What can be done for tubes that do not provide these commas for keep alive current (beside shining a light on them). Can a very high resistor from one cathode be used?

Question 3. Another section talks about biasing idle cathodes.

7. In order to eliminate the glowing halo on idle cathodes, it is recommended

that you provide them with a voltage of plus 60—110 V relative to the cathode

used (indicated).

Is this what the 60v zeners in the 74141 do? Are pullups required? I need some practical tips on connecting the tubes without making the circuit too complicated. The 74141 alone seems to work well with the IN16 without biasing the comma.

[David Forbes]

1. There is no reason that you couldn't run nixies in parallel, other than the maximum current rating of the driver chip.

2. Getting Nixies to light up in the dark can be tricky. My Nixie watches sometimes take a second or so to start glowing in a dark room. A second activation displays normally. Some people install blue LEDs under each tube, which should help.

The 74141 has those Zener diodes to protect the 60V transistors when an invalid code 0xA..0xF is sent to it. The 7441A used a different method to protect the transistors, by decoding all sixteen possible inputs to turn on at least one output transistor.

I have never found a need to add bias resistors to a Nixie circuit. Some feel that it's necessary when multiplexing. They tend to use wires instead of PC boards to connect the tubes, resulting in high capacitance that causes timing issues.

My Nixie watches use the TD62083 50V transistor array, which has commutator diodes that are connected to a 50V tap on the power supply, to give the same protection that the Zeners in the 74141 give.

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[peter bunge]

Thanks David, that was the kind of information I was looking for.

Peter

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[Bill van Dijk]

David,

 

Are you sure Nixies in parallel would work? All of them have slightly different striking voltages, as soon as one strikes, it would draw the voltage too low for the others to strike. Similar to paralleling neon bulbs; that won’t work either.

 

Bill

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[David Forbes]

The cathodes of all paralled Nixies will be pulled to 0 volts. I was assuming that you would use a separate anode resistor for each Nixie tube, because otherwise it wouldn't work for the reason that you state.

On Sat, Jan 2, 2021, 8:20 AM Bill van Dijk <theold...@gmail.com> wrote:

David,

 

Are you sure Nixies in parallel would work? All of them have slightly different striking voltages, as soon as one strikes, it would draw the voltage too low for the others to strike. Similar to paralleling neon bulbs; that won’t work either.

 

Bill

 

 

CAPbqtvfoBYy44903xHKZWfjLsyEXygijfxL3KjGAvaUuFWMSUw%40mail.gmail.com.

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